LOCATION OF MANDIBULAR FORAMEN ON MANDIBLES OF ADULT BLACK SOUTH AFRICAN POPULATION: A MORPHOMETRIC ANALYSIS AND INVESTIGATION INTO

Transcription

1 LOCATION OF MANDIBULAR FORAMEN ON MANDIBLES OF ADULT BLACK SOUTH AFRICAN POPULATION: A MORPHOMETRIC ANALYSIS AND INVESTIGATION INTO POSSIBLE RADIOGRAPHIC CORRELATION. Koketso Tshite A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Masters of Science in Dentistry. Johannesburg, 2017

2 DECLARATION I, Koketso Tshite, declare that this research report is my own work. It is being submitted for the degree of Masters of Science in Dentistry in the University of the Witwatersrand, Johannesburg. It has not been submitted before for any degree or examination at this or any other University.. Signature of candidate day of II

3 DEDICATION This dissertation is dedicated to: The All Mighty God, my Lord Jesus Christ, for in Him I was chosen and have been enriched in every way. My son and daughter: Lukhanyo and Khwezilomso Mbambo. My husband Ntobeko Mbambo, for his ongoing support and immense patience. My parents Moruakgomo and Matshidiso Tshite, for their constant solace during my studies. My sisters Dr Felicia Tshite-Molamu and Ontiretse Tshite, my brothers Percy and Victor Tshite, whose affection, love, encouragement and prayers of day and night enabled me to get such triumph and prestige. My helper Mahlaku Phokwane, for her absolute commitment. III

4 PRESENTATIONS ARISING FROM THIS STUDY Postal presentation at the International Association of Dental Research (IADR) 2016, Cape Town: Morphometric analysis of the location of mandibular foramen in adult black South African population. IV

5 Abstract The objective of the study was to determine the exact location of the mandibular foramen among black South African population using a possible correlation of radiographic and morphometric analysis. Sexual dimorphism in the position of the foramen was taken into consideration. This study was conducted on a total of 253 adult dry human mandible specimens and 24 adult radiographic data from the cone beam computed tomographic records of patients. Both male and female specimens of ages between years old and above were examined for morphometric analysis. The age group for the radiographic analysis was between years old. The length, height and distance of the mandibular foramen in relation to the anterior and posterior border of the ramus of the mandible; superior and inferior border of the mandible as well as the distance in relation to the coronoid & condyle were measured. All the measurements were taken using a mandibulometer and the Dental sliding digital callipers for the morphometric analysis. For both radiographic and morphometric analyses, the distance of the mandibular foramen (MF) to the posterior region of ramus was smaller than that of MF to anterior region. The same pattern of results were observed for both males and females in all age groups. Males generally showed greater readings than females in all parameters, except the MF-P measurement. The MF was situated more towards the superior part of the mandible in the morphometric study. In the radiographic study, the MF was situated more towards the inferior part of the mandible. No significant difference was noted amongst different age groups. With regards to the antero-posterior dimensions of the mandible, the MF was found to be situated more towards the posterior region of the ramus for both radiographic and morphometric analyses in all age cohorts. With regards to infero-superior dimensions of the mandible, the MF was situated more towards the superior part of mandible in the V

6 morphometric analysis, but more towards the inferior part of the mandible in the radiographic analysis. In conclusion, the position of the MF was constant with regards to the anteroposterior dimensions for both radiographic and morphometric analyses. Therefore, this suggests that the chances of finding the MF in the anterior border of ramus of mandible are limited hence the anterior border can be regarded as the safety zone in a South African population. VI

7 ACKNOWLEDGEMENTS A successful project cannot be prepared and achieved by single efforts only or by whom the project is assigned, but it demands the guardianship of some conversant people who assist in the completion of a successful project. I therefore extend my sincere gratitude to my supervisors: Dr Olatunbosun Olaleye, Professor Ejikeme Mbajiorgu and Professor Brian Buch for all their assistance and guidance. Moreover Dr Olatunbosun Olaleye who at all times availed himself for indispensable advice and succour. My gratitude is sincerely expressed further to the following people: My spiritual parents: Apostle Dr Francis Hillary Sakufiwa and Pastor John and Jenny Rose, for their unceasing intercessions which reinforced my faith. Mr Brendon Billings, Curator (Raymond Dart Collection of Human skeletons) in the School of Anatomical Sciences, University of the Witwatersrand, for his bright ideas and advice in morphological anatomy. Mr Adedayo Tunde Ajidahun for his invaluable assistance with the statistical analysis. Dr Tobias Houlton for his assistance with the project pictures. My Head of Department, Dr Daisy Fidelis Kotsane and my departmental colleagues for their comprehension. School of Anatomical Sciences and Wits School of Oral Health Sciences, University of the Witwatersrand, Johannesburg, South Africa for allowing me to conduct my project in their premises. VII

8 TABLE OF CONTENTS DECLARATION... II DEDICATION... III PRESENTATIONS ARISING FROM THIS STUDY... IV Abstract... V ACKNOWLEDGEMENTS... VII TABLE OF CONTENTS... VIII LIST OF TABLES... XI LIST OF ABREVIATIONS... XII APPENDICES:... XIV 1. Chapter one: Introduction Background Aim of the study Objectives of the study Type of study Significance of study Literature review Anatomy and embryology of mandibular foramen Population groups previously studied Significance of the mandibular foramen Limiting factors of a successful inferior alveolar nerve block Complications associated with Orthognathic Surgery Modalities used to determine the position of mandibular foramen Conclusion of literature review Chapter two: Materials and methods The study has two components: Dry bone and CBCT radiographs Site of the study Study population Inclusion criteria for both dry bones and CBCT radiographs: Exclusion criteria for both dry bones and CBCT radiographs: Measuring instruments Data collection for both dry bones and CBCT radiographs: VIII

9 2.7. Data analysis for both dry bones and CBCT radiographs: Ethical consideration Study limitations Source of bias Chapter three: Results Sample size, age and sex stratification Test for normality Distribution of the demographics Morphology measurements of the samples Sex distribution of samples Age distribution of the samples Mean difference in morphometric measurements Distribution of radiographs measurement Comparison between the mean measurements of the radiograph and the morphometric Chapter four: Discussion Morphometric study Radiographic component Comparison between morphometric and radiographic measurements Summary of the discussion Chapter five: Conclusion REFERENCES IX

10 LIST OF FIGURES Figure 2.1: Illustration of some of the measurements carried out in the morphometric study. 9 Figure 2.2: Illustration of some of the measurements carried out in the radiographic study. Internet accessed on 23 March, Figure 2.3: Internal surface of ramus of mandible. MF-A; MF-P; A-P; MF-GO; MF-S Figure 2.4: Internal surface of ramus of mandible. MF-I; MF-H; MF-GO; H-GO Figure 3.1: Histogram showing normal distribution of the morphometric LMF-P data X

11 LIST OF TABLES Table 2.1: Various parameters on the ramus of mandible Table 2.2: Additional parameters in the current study Table 2.3: Age groups of dry mandibles..15 Table 3.1: Shapiro-Wilk test for normality Table 3.2: Demographics of the morphometric samples Table 3.3: Mean of morphology measurement of the total sample Table 3.4: Gender distribution of samples Table 3.5: Age distribution of the morphology Table 3.6: One way analysis of variance (ANOVA) between the age groups Table 3.7: Radiograph measurements of the age cohort Table 3.8: Comparison between the mean measurements of the radiograph and the morphometric XI

12 LIST OF ABREVIATIONS AMFs: Accessory mandibular foramina ANOVA: Analysis of variance CBCT: Cone beam computed tomography GO-M: Distance from the most posterior border of the ramus of mandible to the most anterior point on the menton H-GO: Distance from the highest point of condylar head to the most inferior point on the ramus of mandible IAN: Inferior alveolar nerve IANB: Inferior alveolar nerve block IANVB: Inferior alveolar neurovascular bundle L: Lingula of mandible MF: Mandibular foramen MF-A: Distance from the midpoint of the anterior margin of MF to the nearest point on the anterior border of ramus of mandible MF-GO: Distance from the inferior point of the MF to the furthest point on the inferior border of ramus of mandible MF-H: Distance from the most inferior point of the MF to the highest point on the condylar head MF-I: Distance from the highest point of coronoid notch to the most inferior point on the MF MF-P: Distance from the midpoint of the posterior margin of MF to the nearest point on the posterior border of ramus of mandible MF-S: Distance from the lowest point of sigmoid notch to the inferior point of MF P-A: Distance from the most posterior border of ramus of mandible to the most anterior point on the ramus of mandible S-GO: Distance from the lowest point of sigmoid notch to the most inferior point of ramus of mandible SSO: Sagittal split osteotomy XII

13 SSRO: Sagittal split ramus osteotomy V 3 : Third division of Trigeminal nerve XIII

14 APPENDICES: 1. Appendix 1: Data collection sheet. 2. Appendix 2: Human Research Ethics Committee (Medical). 3. Appendix 3: Wits Oral Health Centre Research Committee. 4. Appendix 4: School of Anatomical Sciences tentative approval letter XIV

15 1. Chapter one: Introduction 1.1. Background The mandibular foramen (MF) is one of the openings found in human mandibles together with mental foramen. MF is located bilaterally and just above the centre of the internal surface of ramus of mandible (Samanta and Kharb, 2013; Thangavelu et al., 2012). However, the exact position of MF varies amongst different population groups (Alves and Deana, 2014; Mbajiorgu, 2000; Olivier et al., 2010; Thangavelu et al., 2012). MF is a very significant anatomical landmark in clinical dentistry because it serves as an entry point for inferior alveolar nerve (IAN) and its accompanying vascular structures known as inferior alveolar artery and vein, which navigate the mandibular canal to provide sensation and blood supply to mandibular teeth (Samanta and Kharb, 2013; Thangavelu et al., 2012). In clinical dentistry, inferior alveolar nerve block (IANB) is a common local anaesthetic given to patients that may require extractions and deep restorations of posterior mandibular teeth, thus, the variations in the position of MF may hinder dental clinicians to achieve a successful inferior alveolar nerve block, which in turn may result in local anaesthetic toxicity as well as damage to inferior alveolar neurovascular bundle (IANVB). Consequently, it is a prerequisite for dental clinicians to be familiar with the position of MF in order to avoid such complications Aim of the study The aim of this study was to determine the location of mandibular foramen in mandibles of adult black South African population and to correlate bony morphometric data with radiographic data Objectives of the study The objectives of this study are: 1. To determine the mean position of MF on radiographs using the cone beam computed tomography (CBCT) and on dry human mandibles of black South African cohort. 2. To determine the influence of sex and age specific differences in the position of mandibular foramen of black South African cohort. 1

16 3. To comparatively analyse data obtained from both radiographic and morphometric measurements by determining any possible correlation Type of study Retrospective and cross-sectional study that included 253 dry human mandibles and 24 CBCT radiographs Significance of study Numerous reports on the failure rate of inferior alveolar nerve block (IANB) as well as damage to inferior alveolar neurovascular bundle (O Ryan and Araujo, 1999) led to morphometric and radiographic investigation into determining the position of MF in various population groups. Results showed differences, amongst males and females of different population and age groups and the conclusions were such that factors as ancestry, sex and age affect the location of MF. There are no published studies thus far in the South African population; therefore, there are no records or data on the position of MF in relation to the different parameters of the ramus of mandible. Furthermore, the use of CBCT in clinical dentistry has become very popular because the images of CBCT are 3 dimensional and they give more precise visualization of the anatomical structures in the maxillofacial region. Thus, this study will provide the South African morphometric data obtained from both dry adult human mandibles and radiographic data obtained from the CBCT radiographs of patients with the purpose of investigating any possible correlation between the two analyses. The outcome of the investigation will therefore facilitate locating the MF in relation to the different borders of ramus of mandible, considering sex and age aspects. The information of which will provide the dental clinicians with the predictable indicators that will assist them to achieve a successful IANB and surgical procedures such as the sagittal split ramus osteotomies (SSRO) without inferior alveolar nerve bundle fatalities Literature review Anatomy and embryology of mandibular foramen Mandibular foramen lies in close proximity to the Lingula (L) of mandible. The lingula is described as a tongue-shaped bone projection on the medial aspect of ramus just anterior to MF, which further continues along the mandibular channel (Lopes et al., 2010 ;Monnazzi et 2

17 al., 2012). Between the 4 th and 8 th week post fertilization, bilateral development of mandibular prominences together with frontonasal and maxillary prominences occur which together give rise to human face (Allan and Kramer, 2002). However, it is only during the 24 th week of intrauterine life that the mandibular foramen and canal form. The mandibular foramen and canal both develop during the process of intramembranous ossification of the body and ramus of mandible, which occurs in the presence of inferior alveolar neurovascular bundle (IANVB) (Alves and Deana, 2014). The shapes of mandibular foramen and canal are completed as the process of ossification progresses (Park and Lee, 2015) Population groups previously studied The exact position of MF has been reported to vary amongst males and females of different population and age groups (Alves and Deana, 2014; Mbajiorgu, 2000; Olivier et al., 2010; Thangavelu et al., 2012). Nonetheless, MF has always been found in the posterior region of the ramus of the mandible (Samanta and Kharb, 2013). The MF is always situated in the ventral and inferior two-thirds of ramus with no differences according to side, sex and age (Olivier et al., 2010). Furthermore, other locations of MF were reported to be the middle part of the ramus, 3 rd quadrant, level of occlusal plane, below the occlusal plane and at midpoint of the ramus of mandible (Mbajiorgu, 2000). A study done in Kenya on the location of the MF showed that 4.7%, 64.6% and 30.7% of the mandibular foramen was located above, below and at the level of the occlusal planes respectively (Roberts and Sowray, 1979). These results were different from the ones discovered in the East Indian population which revealed 2.5%, 75% and 22.5% above the occlusal plane, below the occlusal plane and at the level of the occlusal plane respectively (Nicholson, 1985). It has been discovered that the position of the MF is affected by the degree of the mandibular angle (Gabriel, 1958). The more oblique the angle of the mandible is, the further forward and higher up the MF will be (Gabriel, 1958). A study carried out on 120 mandibles by Marzola et al., (2005), noted that on average the mandible angle is 130 degrees. In 2010, Trost and colleagues reported that the probability of the MF being located either in posterior or superior third of ramus of mandible is very low and they referred to those two regions as the safety zone. The main role of the safety zone is to allow the oral and maxillofacial surgeons to perform SSRO for correction of underlying skeletal abnormalities without damaging the IAN and its accompanying vascular structures (Olivier et al., 2010). 3

18 MF is positioned at an equidistant anteroposterior point relative to ascending ramus; it is 18mm from the anterior border; 17 mm from the posterior border; 21 mm above from the mandibular foramen and 21 mm from the top of the condyle (Marzola, et al., 2005). Since the MF lies in close proximity to the lingula of the mandible, the distance from the mandibular foramen to the upper point of lingula was also examined. Results showed that the average distance of the MF to lingula was 4.8 mm while it was 3.6mm to the midpoint of the line of the shortest distance between the anterior and posterior ramus of the mandible (Martone et al., 1993) Significance of the mandibular foramen MF is a very significant anatomical landmark in clinical dentistry because it serves as an entry point for the inferior alveolar nerve (IAN) and its accompanying vascular structures known as inferior alveolar artery and vein (Thangavelu et al., 2012). The inferior alveolar artery which is a branch of the maxillary artery directs downward and laterally in the pterigomandibular space, accompanied by the corresponding IAN and entering the mandibular foramen (Teixeira et al., 2008). It is very important because as it runs through the mandibular canal, it sends branches to the pulp, bone, and gingiva, therefore, any injury will compromise vascularization of these tissues. The mandibular nerve which is a third division (V 3 ) of the largest cranial nerve called Trigeminal nerve, gives rise to the IAN (Strini et al., 2006). As soon as the inferior alveolar neurovascular bundle enters the mandibular foramen, it traverses the mandibular canal, supplying the mandibular teeth (Samanta and Kharb, 2013). The IAN exits the mandible through the mental foramen, giving sensory branches to the skin and mucosa of the lower lip as well as the gingivae of canine to 1 st mandibular molar (Teixeira et al., 2008). In clinical dentistry, inferior alveolar nerve block (IANB) is a common local anaesthesia given to patients that may require extractions and deep restorations of posterior mandibular teeth (Padmavathi et al., 2014). In order to achieve a successful anaesthesia, a dental clinician is supposed to inject the local anaesthesia around the IAN before it enters the MF. The technique which is used in IANB is called the Halsted technique and the success of this technique depends on placing the tip of the needle close to the mandibular foramen and injecting the local anaesthesia in the pterygomandibular space (Mbarjiorgu, 2000; Padmavathi et al., 2014). 4

19 1.9. Limiting factors of a successful inferior alveolar nerve block The variations in the position of MF may increase the risk of inferior alveolar nerve block (IANB) failure and damage to the inferior alveolar neurovascular bundle (Alves and Deana, 2014; Mbajiorgu, 2000; Olivier et al., 2010; Samanta and Kharb, 2013; Thangavelu et al., 2012). Therefore, if the dental clinicians are not familiar with the position of MF, it will be difficult to achieve a successful IANB and that could also lead to repeated injections which can result in local anaesthetic toxicity (Alves and Deana, 2014; Olivier et al., 2010; Padmavathi et al., 2014; Shuchardt, 1942; Witter et al., 2011; Wolford, 2000) In addition to the variations in the position of MF, the presence of accessory mandibular foramina (AMF) is the other contributing factor even though reported cases on AMFs are very few (Samanta and Kharb, 2013). They can present as single or double and are situated either below or above the mandibular foramen (Padmavathi et al., 2014; Samanta and Kharb, 2013). The IAN may have additional branches that are given off before the IAN enters the MF, therefore, these branches can be associated with the presence of AMFs (Samanta and Kharb, 2013). A radiographic examination of AMFs was done by passing a metallic wire through them. The results showed that the neurovascular bundle passing through the examined AMF supplied the root of the third molar (Das and Suri, 2004). Consequently, the mandibular molar teeth can be supplied by the additional branches of IAN, which enter the mandible through the AMFs (Padmavathi et al., 2014; Samanta and Kharb, 2013). Hence, it is essential that the knowledge on the absence or the presence of the AMFs is in place and is understood. High failure rates of IANB can be attributed to local anaesthesia given in the presence of AMFs, whereby nerves such as mylohyoid and buccal may enter through the AMFs and resulting in insufficient anaesthesia of the IAN; and can also be due to additional branches of IAN passing through the AMFs and escaping the local anaesthesia (Samanta and Kharb, 2013; Padmavathi et al., 2014). AMFs can be a site for the spread of tumours following radiotherapy as well as providing a route for the spread of infection. The knowledge of AMFs can give important information on the branching pattern of IAN which can assist the dental clinicians with avoiding complications (Samanta and Kharb, 2013; Padmavathi et al., 2014). The manner in which the IAN divides may show several differences inside the mandibular canal (Samanta and Kharb, 2013). It can either traverse the mandibular canal as a single trunk providing branches to molar and premolar teeth or giving off a major and smaller trunk near 5

20 the MF. Subsequent to traversing through the mandibular canal, the major trunk exits the mandible through the mental foramen whereas the smaller trunk turns into the incisive nerve Complications associated with Orthognathic Surgery Sagittal split osteotomy (SSO) or sagittal split ramus osteotomy (SSRO) is a popular dental surgical technique which is used to correct mandibular deformities such as prognathism and retrognathism (Alves and Deana, 2014; Shuchardt, 1942; Trost et al., 2010; Witter et al., 2011; Wolford, 2000). It was first introduced by Shuchardt in 1942 but was modified and improved by Trauner and Obwegeser in 1957 (Witter et al., 2011). A similar surgical technique to the SSO is referred to as an intraoral vertical ramus osteotomy (IVRO) but was described as being less advantageous in correcting mandibular deformities as compared to the SSO (Wolford, 2000). The advantages of SSO in conjunction with rigid fixation (RF) include simultaneous extraction of the impacted third molars with high levels of postoperative comfort. However, even though the SSO or SSRO was deemed advantageous, various complications and disadvantages associated with it, such as undesirable fractures, haemorrhage, injury to the neurovascular bundle, bone necrosis, infection and relapse can occur (Araujo, 1999; Dolce et al., 2002; Fernandes et al., 2009; Vansickels et al., 1988; Wolford, 2000;). The SSO is performed in close proximity to the IAN, therefore, if the IAN is injured post- operative neurosensory disturbances can occur; and 30-40% of such neurosensory disturbances develop in the lower lip and the mental skin (Witter et al., 2011). This is because during the SSO the IAN can be cut by drill, a saw or chisel during the separation of the fragments, which leads to post-operative neurosensory complications. Furthermore, IAN could also be stretched or removed from its location at the time of medial displacement or injured by compression of the segments during fragment fixation (O Ryan and Araujo, 1999) Modalities used to determine the position of mandibular foramen The importance of preoperative Cone Beam Computed Tomography (CBCT) scans has been emphasized since it offers the surgeon the opportunity to locate the neurovascular bundle in three dimensions (Agbaje et al., 2013; Park and Lee, 2015). Those dimensions allow for individual modification of the approach of the lower border of ramus of mandible and the buccal plate, therefore, avoiding injury to the inferior alveolar neurovascular bundle. A panoramic radiograph is a 2 dimensional image which lacks the information in the bucco- 6

21 lingual dimension and also magnifies both the vertical and the horizontal directions (Agbaje et al., 2013; Park and Lee, 2015). Thus, panoramic radiographs do not allow the clinician to predict whether the inferior alveolar nerve is close to the lingual or to the buccal cortex. With CBCT imaging, the course of the inferior alveolar nerve and its relationship to surrounding vital structures can be readily observed (Agbaje et al., 2013; Farzaneh et al., 2013). CBCT images provide vital pre-operative information about the structures in and around the operating site as well as more precise visualization of the anatomical structures in the oral region (Agbaje et al., 2013; Farzaneh et al., 2013) Conclusion of literature review There are no records that the position of the MF has been studied in South Africa, however, published records are available for various countries. The position of MF has been recorded to vary amongst different people and the contributing factors to these variations have been reported to be race, sex, and age (Ennes et al., 2009; Mbajiorgu, 2000; Oguz et al., 2002). Therefore, there is a possibility that different results will be achieved in South Africa and this study is very pertinent because of the diversity of racial groups in South Africa. The aim of this study is to radiographically and morphometrically determine the position of the MF using CBCT radiographs of patients and dry adult human mandibles, in Black South African cohort and also identify any possible link that has not been reported between both analyses. 7

22 2. Chapter two: Materials and methods 2.1. The study has two components: Dry bone and CBCT radiographs. Site of the study Dry bone component: It was conducted in the Raymond A Dart Bone collection in the School of Anatomical Sciences, University of the Witwatersrand, Johannesburg, South Africa. Radiographic component: It was conducted in the Maxillofacial and Oral Radiology Department of Charlotte Maxeke Johannesburg Academic Hospital, South Africa Study population Dry bones: This was a retrospective, cross-sectional study carried out on a total of 253 Adult Black South African dry human mandibles. There were 120 female specimens and 133 male specimens. The female to male ratio was 0.9:1. CBCT Radiographs: This was a retrospective, cross-sectional study consisting of a total of 24 CBCT radiographic data of Adult Black South African patients. The records were from the year 2011 to 2016, which included 15 male records and 9 female records Inclusion criteria for both dry bones and CBCT radiographs: a) Male and female dry mandible samples of ages ranging between years old and above. b) Fully or partially dentate (minimum of 6 teeth in the entire mandible) dry mandibles including the second molar (teeth 37 and 47) Exclusion criteria for both dry bones and CBCT radiographs: a) Completely edentulous mandibles b) Mandibles with evident deformity or pathology c) Mandibles that have undergone surgery d) Damaged (e.g. fractured) mandibles 8

23 2.5. Measuring instruments Dry bone component: The height and length of mandible were measured using a mandibulometer, and for all linear measurements a dental sliding digital callipers (Mitutoyo, accuracy of 0.01mm was utilized). The measurements obtained were entered into a data collection sheet. Figure 2.1: Illustration of some of the measurements carried out in the morphometric study Radiographic component: A Galaxis software measuring ruler was used for all the measurements. Linear measurements and the height were calculated on the tangential section and the length was calculated on the axial section. The CBCT images were obtained from the Sidexis data base on a Galileos 3D comfort by Sirona Dental systems. All radiographs were obtained from the same machine with the following information: model: Galileos GAX 5 (Compact); serial no: Records of the field of view of the mandible were examined. All CBCT generated mandibular images were first increased to a thickness of 300% before measurements were undertaken and a U-jaw mandible shape was maintained in all the images. 9

24 Figure 2.2: Illustration of some of the measurements carried out in the radiographic study. Internet accessed 23 March, Data collection for both dry bones and CBCT radiographs: A repeatability/ intra-observer test was done at the beginning of the morphometric study. The rationale for the test was to make sure that the same methods and techniques are used with an intension of achieving significant results. However, no intra-observer test was done on the radiographic study. Various osteological landmarks illustrated in Figure 2 & 3 were used to locate the MF. However, six additional landmarks were introduced in the current study. The current study adopted the technique by Samanta and Kharb (2013). Bilateral measurements of the mandible were taken separately. MF was the point of reference in all the measurements. To precisely locate the MF, the following parameters were measured: 1) Distance from the midpoint of the anterior margin of MF to the nearest point on the anterior border of ramus of mandible (MF-A, table 1) 2) Distance from posterior margin of MF to the nearest point on the posterior border of ramus of mandible (MF-P, table 1) 10

25 3) Distance from the lowest point of sigmoid notch to the inferior point of MF (MF-S, table 1) 4) Distance from the inferior point of the MF to the furthest point on the inferior border of ramus of mandible (MF-GO, table 1) In the current study six additional landmarks were measured: 1) Distance from the highest point of condylar head to the most inferior point on the ramus of mandible (H-GO, table 2) 2) Distance from the highest point of coronoid notch to the most inferior point on the MF (MF-I, table 2) 3) Distance from the most inferior point of the MF to the highest point on the condylar head (MF-H, table 2) 4) Distance from the most posterior border of the ramus of mandible to the most anterior point on the menton ( GO-M, table 2) 5) Distance from the most posterior border of ramus of mandible to the most anterior point on the ramus of mandible (P-A, table 2) 6) Distance from the lowest point of sigmoid notch to the most inferior point of ramus of mandible (S-GO, table 2) Figure 2.3: Internal surface of ramus of mandible. MF-A; MF-P; A-P; MF-GO; MF-S. 11

26 Figure 2.4: Internal surface of ramus of mandible. MF-I; MF-H; MF-GO; H-GO. The dry bones were divided into age groups of 5 years apart (refer to table 3.2), with the purpose of identifying any evident morphological changes. In the radiographic study only one age group of years old was examined, and this was due to unavailability of CBCT radiographs that could not meet the inclusion criterion. The selected radiographs were also of Black South African cohort, however, not of the same ethnic groups as in the morphometric study. Classification of ethnicity in the radiographic study was biased. The first name of the patient was used to classify the ethnicity. 12

27 Table 2.1: Various parameters on the ramus of mandible ANATOMICAL LANDMARK DEFINITION REFERENCE INSTRUMENT MF-P Distance from the MF to Nilton et al., 2014 Dental sliding digital posterior border of ramus calliper MF-A Distance from the MF to Nilton et al., 2014 Dental sliding digital anterior border of ramus calliper MF-S Distance from the MF to Nilton et al., 2014 Dental sliding digital sigmoid notch calliper MF-GO Distance from MF to inferior Nilton et al., 2014 Dental sliding digital border of ramus calliper 13

28 Table 2.2: Additional parameters in the current study ANATOMICAL LANDMARK DEFINITION REFERENCES INSTRUMENT S-GO Distance from the sigmoid Park and Lee, 2015; Dental sliding digital notch to inferior border of Thangavelu et al., calliper ramus 2012 MF-I Distance from the MF to the Current study Dental sliding digital highest point on the coronoid calliper process MF-H Distance from the MF to the Thangavelu et al., Dental sliding digital highest point on the condylar 2012 calliper process H-GO Distance from the highest point Current study Mandibulometer on condylar head to the inferior border of ramus GO-M Length of mandible from the Current study Mandibulometer GO to the most anterior point on the menton P-A Distance from the posterior Current study Dental sliding digital border of ramus to anterior calliper border of ramus 14

29 Age groups: All specimens were categorized into male and female and then divided into the following nine age groups with 5 years apart: Table 2.3: Age groups of the dry mandibles Variables N Age (years) >56 30 Gender Female 120 Male 133 The initial proposition of the current study was to have fifteen specimens in each age cohort, however, due to some of the specimens not meeting the inclusion criteria, some age cohorts ended with less subjects Data analysis for both dry bones and CBCT radiographs: Descriptive statistics of mean, standard deviation and frequency was used to summarize the data. Paired t-test and one way Anova tests were used to compare group means of morphology measurements and total population, in the specific age cohorts. A Shapiro-Wilk test was used to check the normal distribution of data. The degree of magnification and distortion in the radiographic study was calculated. The difference between the two readings as a ratio of the true reading expressed as a percentage indicated the magnification for each parameter. The average magnification was taken as the standard error of all the magnifications. The percentages of either or both was set to be disregarded if less than 5% and therefore, level of significance for both radiographic and morphometric studies was set at p<0.05.unfortunately the average magnification did not conform to the expected norm for the CBCT machine used. 15

30 2.8. Ethical consideration Dry bones: Ethical clearance was obtained in the year 2015 from the Ethics committee of the School of Anatomical Sciences as well as Human Research Ethics Committee of University of the Witwatersrand, Johannesburg, South Africa to utilize the human dry mandibles in the Raymond A Dart Bone collection. CBCT radiographs: Ethical clearance was obtained from the Wits Oral Health Centre Hospital Research committee, to use the CBCT radiographic data in Oral Radiology Department of Charlotte Maxeke Johannesburg Academic Hospital Study limitations Dry bones: Due to some specimens not meeting the inclusion criteria, some age cohorts ended up with fewer subjects than planned. Total sample sizes of 253 dry bones were examined. CBCT radiographs: Due to failure of most radiographs not meeting the requirements of the inclusion criteria, only 24 records were examined. The analysed sample size consisted of 9 female records and 15 male records, in the age cohort of years old. Most of the patients that were referred for CBCT radiographs, had some form of oro-facial pathology, hence many radiographs were excluded Source of bias Unlike the selection of specimens according to race and ethnicity in the Raymond A Dart Bone collection catalogue, selection of radiographic data was a bit biased. This was due to the fact that when patients first consulted Wits Oral Health Centre, they are registered into the Hospital system, and their ethnicity or race is classified according to their first language. South Africa is a diverse country with many ethnicities and interracial marriages. That made it a little difficult to precisely classify some of the subjects. 16

31 3. Chapter three: Results 3.1. Sample size, age and sex stratification A total sample size of 277 subjects was used in this study. This included 253 adult dry human mandibles and 24 CBCT radiographic records of patients. The samples were further stratified according to sex and sub age groups ranging from years old and above in the morphometric study, however, in the radiographic study, only one age cohort of years was used due to the unavailability of records that met the inclusion criteria 3.2. Test for normality The Shapiro-Wilk test for normality was conducted and majority of the morphometric measurements showed normal distribution as shown in Table 3.1. Table 3.1: Shapiro-Wilk test for normality Statistic Sig. LEFT MF-P MF-A P-A MF-S MF-GO S-GO MF-I MF-H H-GO GO-M RIGHT MF-P MF-A P-A MF-S MF-GO S-GO MF-I MF-H H-GO GO-M

32 Figure 3.1: Histogram showing normal distribution of the morphometric MF-P data on the left side. 18

33 3.3. Distribution of the demographics Table 3.2 outlines the demographic properties (sex and age cohorts) of the mandibles. In the morphometric study from a total sample size of 253, 120 were females (47.4%) and 133 males (52.6%). The age group (51-55 years) contained the least number of specimens making 7.5 % of the total population. Table 3.2: Demographics of the morphometric samples Variables N % Age > Gender Female Male

34 3.4. Morphology measurements of the samples Table 3.3 shows the mean and standard deviation of the morphometric measurements on the right and left sides of the mandible. The mean of the MF-P; MF-I; and H-GO were significantly increased on the right hand side with the p< There was no significant difference on the rest of the measurements. Table 3.3: Morphology measurement of cohort irrespective of sex Right Left Mean SD Mean SD Sig MF-P ** MF-A P-A MF-S MF-GO S-GO MF-I ** MF-H H-GO ** GO-M *p<0.05, **p<

35 3.5. Sex distribution of samples Table 3.4 outlines the means morphometric measurements according to gender distribution and the comparative analysis on the right and left sides. There was a significant difference between males and females in almost all the measurements except for the MF-P on the right and the MF-P and MF-S on the left (p>0.05). Males showed significantly higher readings than females on both the left and right side in all parameters except for the female MF-P on the right (p>0.05). In both males and females, the right side demonstrated higher readings than the left side. 21

36 Table 3.4: Parameter variations with sex Male Female Mean SD Mean SD Sig Right MF-P Left Right MF-A Left Right P-A Left Right MF-S Left Right MF-GO Left Right S-GO Left Right MF-I Left Right MF-H Left Right H-GO Left Right GO-M Left *p<0.05, **p<

37 3.6. Age distribution of the samples Table 3.5 on page 24 outlines the age distribution of the morphometric measurements on both the left and the right sides. The left and right P-A distance was at its highest point at the age of years and at its lowest point at the age of years. MF-A reading was higher than the MF-P distance in all the samples irrespective of age. MF-S; MF-GO and S-GO increased significantly with increasing age in all the age cohorts on both left and right sides (p<0.05). 23

38 Table 3.5: Age distribution of the morphology >56 Right Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD MF-P MF-A P-A MF-S MF-GO S-GO MF-I MF-H H-GO GO-M >56 Left Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD MF-P MF-A P-A MF-S MF-GO S-GO MF-I MF-H H-GO GO-M

39 3.7. Mean difference in morphometric measurements Table 3.6 shows the significant difference between the age cohorts for the morphometric measurements. There was a significant difference in the P-A measurement on both the right and left sides and MF-S measurements on both left and right sides (p<0.05). Table 3.6: One way ANOVA between the age groups Right Left F Sig F Sig MF-P MF-A P-A * * MF-S * * MF-GO S-GO MF-I MF-H H-GO GO-M *p<

40 3.8. Distribution of radiographs measurement Table 3.7 shows the demographic distribution of the years age cohort. Males showed significantly higher readings than females in all the parameters on both left and right sides except for the MF-P measurement. Radiographic measurements of the MF-GO, S-GO, MF-I and H-GO showed a significant difference between males and females on the right side (p<0.05). Except for the MF-A, the mean measurement of all other parameters showed no significant difference between males and females (p>0.05). Table 3.7: Radiographic measurements of the age cohort. Male Female Right Mean SD Mean SD Sig MF-P MF-A P-A MF-S MF-GO * S-GO * MF-I * MF-H H-GO * GO-M Left Mean SD Mean SD Sig MF-P MF-A * P-A MF-S MF-GO S-GO MF-I MF-H

41 H-GO GO-M Comparison between the mean measurements of the radiograph and the morphometric Table 3.8 outlines the comparison between the means for the radiographic and morphometric measurements in the age cohort There was a significant difference on the right side on almost all parameters except the MF-GO; S-GO; MF-I and MF-H (p>0.05). The left side also showed significant differences in all parameters except for the MF-S; MF-GO and MF-I (p 0.05). 27

42 Table 3.8: Comparison between the mean measurements of the radiograph and the morphometric Morphology Radiograph Right Mean SD Mean SD Sig MF-P MF-A P-A MF-S MF-GO S-GO MF-I MF-H H-GO GO-M Left Mean SD Mean SD Sig MF-P MF-A P-A MF-S MF-GO S-GO MF-I MF-H H-GO GO-M

43 4. Chapter four: Discussion This present study aimed to determine the position of mandibular foramen in relation to mandibular osteological landmarks, using morphometric and radiographic measurements. It was conducted in the South African adult black population utilizing dry bony mandibles and CBCT radiographs, which were categorized into sex and age cohorts years old and above, at five year intervals. The morphometric results of the current study corroborate with earlier reports on similar studies done in other populations of different countries (Alves and Deana, 2014; Mbajiorgu, 2000; Olivier et al., 2010; Samanta and Kharb, 2013; Thangavelu et al., 2012); however, the radiographic results did not show much of corroboration with other studies. The reason for such a discrepancy in the radiographic study could be attributed to a small sample size used in the current study because, due to unavailability of required radiographic records, only one age group of years old was examined. Another possible reason could be due to limited reports on the study of this kind. Even though there was not enough radiographic data, the two current studies were compared using only one age group of years old with the aim of determining any possible correlation. This is a first study of its kind; in that, no published studies are available on the South African population. The results of the two components were analysed and separately discussed below Morphometric study In the morphometric study from a total sample size of 253, 120 were females (47.4%) and 133 males (52.6%). The age group (51-55 years) contained the least number of specimens making 7.5 % of the total population. Some of the reasons ascribed to so small a percentage in the year- old age cohort were either because the second molars in that group (teeth 37 and 47) were missing or the mandibles were completely edentulous. A comparison of the left and right sides of the total sample showed a statistically significant difference only in the MF-P; MF-I and H-GO with (P<0.001). The right side showed higher readings than the left in all parameters except in the MF-A and P-A measurements with no significant diffrence (refer to Table 3.3). An analysis of the antero-posterior dimension of the mandible showed the mean of MF-P on both left and right sides to be significantly less than the mean of MF-A (refer to table 3.3). The mean of MF-A was 18.8mm on the right and 18.9mm on the left whereas the mean of MF-P was 13.7mm on the right and 13.4mm on the left. This suggests that the position of MF on dry bones was more towards the posterior border of the ramus of mandible than towards the anterior border. The results of the current study aligned themselves with that of: Alves and Deana (2014); Marzola et al., (2005); Mbajiorgu (2000); Shalini et al., (2016); and Thangavelu et al., (2012), but differed 29

44 slightly from the results of Samanta and Kharb (2013). Samanta and Kharb (2013) described MF to be at a mean distance of 15.72mm on the right and 16.23mm on the left from the anterior border of ramus of mandible; and at a mean distance of 13.29mm on the right and 12.73mm on the left from posterior border of ramus of mandible. Although there was a slight difference in Samanta and Kharb s study (2013), a similar pattern of MF being situated more towards the posterior border of ramus of mandible was still observed. One possible reason that could be attributed to such a difference might have been the small sample size of sixty mandibles that were utilized in their study. Since two of the objectives in the current study were to determine age- and sex-specific differences, these categorical variables were important factors that were clearly described and considered. However, in earlier studies, these two factors were not always taken into consideration. In a study conducted by Alves and Deana (2014) on 185 macerated mandibles, age, sex and race were clearly described. In their study, the samples comprised both black and white individuals and a significant difference in MF-A and MF-P measurements was noted between the two races. However, the results of their black population group corroborated with the results of the current study on the same parameters. Considering ethnic groups, the results of their study confirmed that differences exist in the parameters studied, in that blacks showed higher values. All specimens utilized by Mbajiorgu (2000) and belonging to the black Zimbabwean population group were all above 25 years old but sex was not taken into consideration. In the study done by Marzola et al., (2005); Samanta and Kharb (2013), Shalini et al., (2016) and Thangavelu et al., (2012), both sex and age of the specimens were unknown. However, the results of the current corroborated with these studies. In both the current study as well as those studies discussed above, the results of MF-A and MF-P parameters suggested that MF was located more towards the posterior border of the ramus of mandible3. However, these finding were contrary to the findings by Trost et al., (2010) which considered the posterior border of the mandible as the safety zone. One possible reason for the difference between the findings by Trost et al., (2010) and the current study may be due to the different methods used. Trost et al., (2010) analysed the position of MF on panoramic radiographs compared to the morphometric methods used in the above discussed studies. Two infero-superior dimensions of the mandible were considered in the current study. Both the sigmoid notch and the condyle constituted the superior part of the mandible. The study showed the mean of MF-GO on both left and right sides to be higher than the mean value of MF-S. The average MF-GO distance was recorded as 22.9mm on the right and 22.7mm on the left; the right side 30